Beverages and other comestibles are often processed and packaged in synthetic polymeric packaging on mechanized conveyor systems which are lubricated to reduce friction between the packaging and the load bearing surface of the conveyor. The lubricants commonly used on the load bearing surfaces of these conveyor systems, such as those used in the food processing, beverage and the brewery industries, typically contain fatty acid soaps as the active lubricating ingredient because of the superior lubricity provided by fatty acid soaps.
The fatty acid soaps are generally formed by neutralizing a fatty acid with a caustic compound such as alkali metal hydroxide (NaOH or KOH) or an alkanolamine (MEA, DEA or TEA). Fatty acid soaps neutralized with such caustic compounds are generally incompatible with polyethylene terephthalate to such an extent that prolonged contact frequently results in the formation of stress cracks and fissures in the plastic. This is most frequently observed in bottling plants where carbonated beverages are placed into polyethylene terephthalate bottles because of the stress placed upon the bottle by the bottling process, the carbonated beverage contained within the bottle, and interval pressure.
Various polyethylene terephthalate compatible lubricant compositions have been developed by replacing at least a portion of the fatty acid with other lubricating components. For example, Rossio, U.S. Pat. No. 4,929,375, suggests that incorporation of a tertiary amine, such as a (C.sub.8-10) alkyl dimethyl amine, into a fatty acid lubricant composition enhances the polyethylene terephthalate compatibility of the lubricant composition.
While these various attempts have been successful in producing lubricant compositions which are compatible with polyethylene terephthalate, such compositions have not generally been effective for providing both superior lubricity and superior compatibility with synthetic polymeric packaging materials. Accordingly, a substantial need still exists for a conveyor lubricant which provides a combination of superior lubricity and compatibility with synthetic polymeric packaging materials.